Marriott owns hotels, but they don't own every hotel with a Marriott brand on top.
Hotel "brands" can NOT dictate providers AT ALL. To do so runs afoul of anti-trust law. They CAN issue a "brand standard" that you have to have WiFi, and it has to be at least "this good" (insert specification).
Now, where the hotels are OWNED (by any party) the OWNER can dictate whatever the hell she wants.
And Marriott most certainly does own a large percentage of the hotels that sport their brand.